Bengaluru: A new study published this week in an international medical journal stated that drinking any hot beverage daily such as tea or coffee above a temperature of 60°C can increase the risk of cancer.
According to the study, drinking over 700 ml of hot tea daily can increase the risk of oesophageal cancer by 90 per cent. Oesophageal cancer happens when abnormal cells in the food pipe (oesophagus) grow in an uncontrolled way.
The study, which has been published in the International Journal of Cancer, was conducted on more than 50,000 people in Golestan, in northeastern Iran. The team of researchers monitored the habit of drinking beverages of 50,045 people, aged between 40 and 75 years, for a period of over 10 years. Between 2004 and 2017, the researchers detected 317 new cases of oesophageal cancer.
In the past, there have been multiple studies, pointing out the link between warm beverages and oesophageal cancer. Even the World Health Organisation (WHO) has stated that very hot beverages of any kind can raise the risk of cancer.
However, this is the first study to point out the exact temperature beyond which the risk of cancer increases manifold.
This is pertinent to not just Indians, who love their morning tea or filter coffee, but also to countries that experience harsh winters.
In many cultures, warm drinks, including alcohol, are often drunk from a samovar (a metal container traditionally used to heat and boil water). In places like Turkey, Russia, China, South America, and Iran, it is very common to consume piping hot beverages that are tea infusions.
“According to our report, drinking very hot tea can increase the risk of oesophageal cancer, and it is therefore advisable to wait for the hot beverages to cool down before drinking it,” said Dr. Farhad Islami of the American Cancer Society and the study’s lead author to CNN.
What is oesophageal cancer?
Oesophagus is our food pipe. It carries the food from the mouth to the stomach. When oesophageal cancer is caused, there are abnormal food pipe cells that grow in a rapid and uncontrolled manner.
It commonly occurs to people aged above 60 years. The risk of this type of cancer is also increased by smoking, and if more than 14 glasses of alcohol are consumed in a week. This is the eighth most common cancer in the world and is almost always fatal, killing about 4,00,000 people a year, according to the International Agency for Research on Cancer.
Ironically, radiotherapy for other cancers such breast cancer, lung cancer, or throat cancer, increases the risk of oesophageal cancer.
What are the symptoms?
There are several persistent symptoms of oesophageal cancer. This includes difficulty in swallowing food, indigestion, throat pain, weight loss, heartburn, and a violent and permanent cough.
All of these are created by repeated scalding, abrasion and irritation of the lining of the oesophagus due to smoke, alcohol and hot liquids.
Dr. James Doidge, a senior research associate at University College London, said that hot drinks were an already established risk factor for oesophageal cancer.
“It doesn’t take a scientist to appreciate that repeated irritation of any body surface increases your risk of cancer. Sunburn gives us skin cancer, smoking gives us lung cancer, and many foods and drinks contribute to the risk of gastrointestinal cancers,” Doidge said.
“Microwaved jam has been known to cause oesophageal injury. It is possible that the trauma leads to cell changes and hence to cancer,” Stephen Evans, a pharmacoepidemiologist at the London School of Hygiene & Tropical Medicine, told the Science Media Center.
Temperature above 60°C is harmful
In most parts of the world, it is common to serve coffee and tea, including herbal teas, at temperatures between 70°C and 80°C. Temperatures above 60°C are harmful to even keratinocytes, the cells that produce keratin, which makes up the outer layer of our skin.
Warm drinks release endorphins and make us friendlier towards other people, studies have shown.
However, when it comes to nutrition, the benefit is in the contents of the tea or beverage, not in its temperature. Several studies on this subject have found people drinking green or black tea, and these teas are known to be consumed when they are cold provided they are steeped long enough. Even alternative cold water steeping to prepare these beverages is practised.
“This is definitely not a ‘scare’ story when placed in the wider context, but avoidance of extremely hot drinks will have possibly beneficial health effects,” said Evans.